A. Field of the Invention
The present invention relates to duct work used to convey air to heat, ventilate or air condition (HVAC) commercial, industrial and residential buildings. More particularly, the invention relates to an apparatus for use in the fabrication of air turning vane and rail structures having a plurality of vanes, fastened between a pair of rails, which are used to smooth air flow in HVAC ducts.
B. Description of Background Art
Flowing air used to ventilate, heat, or cool buildings is typically routed through a network of interconnected, elongated tubes or ducts which are collectively referred to as duct work. The ducts may have a rectangular, round or oval cross section. Changes in the orientation or directional bearing of ducts are usually effected by coupling a pair of ducts together by means of an angled transition section or elbow. These are bent at an angle, typically of 90 degrees, and have rectangular or circular openings for attachment to separate upstream and downstream ducts oriented at the particular bend angle with respect to one another.
When air flowing through a duct impacts a side wall of an elbow or transition section which is disposed perpendicularly to the flow direction, substantial turbulence may be created in the flowing air mass, even when the flow velocity is relatively modest. This turbulence impedes air flow, causing an increase in static pressure and pressure loss coefficients, thus necessitating the use of larger blowers that consume increased drive power, to maintain a given air flow rate at the outlet of the elbow section. Moreover, undesirable vibration and noise may be generated within the duct work, if the turbulence is sufficiently great.
For the reasons stated above, HVAC elbows or transition sections often are fitted with internal air turning assemblies which minimize turbulence by encouraging laminar flow within the elbow. Air turning assemblies designed to be installed within ventilation elbows to minimize turbulence typically employ a plurality of curved, parallel blades or turning vanes spaced apart at regular intervals, to promote laminar air flow where the direction of air flow changes within the elbow. Typical turning vane structures are fabricated from a plurality of curved sheet metal vanes fastened between a pair of flat, parallel metal sheets, often referred to as rails. Usually, such air turning vane and rail structures are fabricated externally, shipped to a job site, and secured within an angled transition section or elbow as required.
Turning vane assemblies which employ a variety of techniques for fastening turning vanes to rails has been disclosed in the following U.S. patents:
Steffens, U.S. Pat. No. 2,292,246, Aug. 4. 1942, Duct Turn, Speiser, U.S. Pat. No. 2,826,221, Mar. 11, 1958, Duct Devices, Gracer, U.S. Pat. No. 2,861,597, Nov. 25, 1958, Air Guide Device, Gracer, U.S. Pat. No. 2,861,597, Nov. 25, 1958, Air Guide Device, Perlin, U.S. Pat. No. 2,884,956, May 5, 1959, Air Guide Device, Gracer, U.S. Pat. No. 2,959,195, Nov. 8, 1960, Air Guide Device, Chesser, U.S. Pat. No. 3,050,160, Aug. 21, 1962, Sheet Metal Connection And Method For Effecting Same, Noll, U.S. Pat. No. 3,075,450, Jan. 29, 1963, Cap Assembly, Bohannon, U.S. Pat. No. 3,144,204, Aug. 11, 1964, Centrifugal Blower Wheel, Olmsted, et al., U.S. Pat. No. 3,224,668, Dec. 21, 1965, Blower Wheel Wedged End Blade Mounting, Jacobsen, U.S. Pat. No. 3,381,713, May 7, 1968, Turning Vane And Rail Construction, Harper, U.S. Pat. No. 3,405,737, Oct. 15, 1968, Duct Device, Hinden, U.S. Pat. No. 3,494,379, Feb. 10, 1970, Air Turning Assembly And Mounting Rail, Hinden, U.S. Pat. No. 3,602,262, Aug. 31, 1971, Air Turning Assembly, Myers, U.S. Pat. No. 4,467,829, Aug. 28, 1984, Turning Vane Rail, DeLord U.S. Pat. No. 4,641,684, Feb. 10, 1987, Rail For An Air Turning Vane Assembly, Myers, U.S. Pat. No. 4,911,205, Mar. 27, 1990, Apparatus And Method For Duct Vane Mounting, Felson, U.S. Pat. No. 5,068,957, Dec. 3, 1991, Turning Vane Setting Tool, Lyons. et al., U.S. Pat. No. 5,181,314, Jan. 26, 1993, Apparatus For Manufacturing Air Turning Assembly.
Vane and rail assemblies known to the present inventors, including those cited above, generally require that mating portions of sheet metal vanes or rails which are to be joined together be deformed by robustly pounding parts thereof, using either a hammer, chisel, or specially designed tools, to fasten the vanes and rails together. Sometimes, pounding on a vane and rail assembly to install a series of vanes can loosen the fastening of vanes installed earlier. Then, when a completed vane and rail assembly has been installed into a duct work elbow; and the latter installed in a building, variations in the pressure of air flowing through the duct work can cause the "cheeks" or walls of curved transition sections to expand and contract, and perpendicular duct walls to flex inward and outward or "oil-can" in response to air pressure fluctuations. Since environmental control systems for buildings require that air flow be turned on and off intermittently, or varied by control dampers, duct work air turning vane assemblies are routinely subjected to such wall deformations. As a result, vanes which had been initially loosened during the fabrication of a turning vane and rail assembly can become completely detached from the rails long after duct work has been installed in a building. As can be readily appreciated, replacing dislodged turning vanes can be an extremely time consuming, laborious and expensive process, particularly in high-rise buildings.
Partly in response to limitations of prior art air turning vane and rail assemblies, the present inventors developed improved air turning vane and rail assemblies of simplified construction and greater versatility than existing assemblies, in which vanes self-lock into engagement with rails, thereby minimizing the likelihood of vanes dislodging from a vane and rail assembly. Those improved turning vane and rail assemblies are disclosed in the present inventors co-pending application Ser. No. 08/912,385, now U.S. Pat. No. 5,927,339, filed Aug. 18, 1997 now U.S. Pat. No. 5,927,339, issued Jul. 27, 1999. The disclosure of that application is hereby incorporated by reference into the present disclosure.
An embodiment of an air turning vane and rail assembly according to the co-pending disclosure includes a pair of laterally spaced apart parallel rails. Each of the rails has a plurality of longitudinally spaced apart, generally trapezoidally-shaped tabs, each bent perpendicularly inwardly towards the opposite rail from a separate perforation through the rail. Each of the upstanding tabs has through its thickness an aperture located near the base of the tab. A plurality of self-gripping double air-foil vanes lockingly engage the tabs, each vane having a generally hemispherically shaped protuberance which protrudes forward through the aperture from a rear concave air-foil plate towards a front convex airfoil plate. In this embodiment the protuberance has an inner flat, transversely disposed lip which locks against the upper wall of the aperture through the tab, when the tab is forcibly inserted into the opening between the front and rear airfoil plates of a vane.
In other co-pending patent applications, Ser. No. 09/129,507 filed Aug. 5, 1998 and Ser. No. 09/153,205, filed Sep. 15, 1998. the present inventors disclosed a Method and Apparatus For Making Self-Gripping Air Turning Vanes of the type described in application Ser. No. 08/912,385.
The present invention was conceived of to provide an apparatus for assembling air turning vanes and rails, particularly those described in application Ser. No. 08/912,385, into finished air turning structures.